Pronounced as 'croo-een-ya', with the emphasis on the -een-.
the Pictish Cruithne
Although appearing in the Pictish Chronicle as the founding father of the Picts in reality Cruithne is the name of a people the Cruthini. Considered to be the Goedelic variant of Priteni or Pritani, as the inhabitants of Britain were originally called. (Alhough later Roman writers from Julius Caesar onwards, preferred Britanni from whence is derived Britannia, Britain, British et al.)
the Astronomical Cruithne
Cruithne is also the name for asteroid 3753, or 1986 TO, the Earth companion or near-Earth asteroid that is co-orbital with the Earth and is sometimes known as "Earth's second moon"
The asteroid itself was discovered by D. Waldron, working with R. McNaught, M. Hartley and M. Hawkins at the Siding Spring Observatory, Coonabarabran, Australia in October 1986; but it was Paul Wiegert, Kim Innanen and Seppo Mikkola who established its co-orbital nature and
published their findings in the science journal Nature in June 1997. Two more near-Earth asteroids, 1998 UP1 and 2000 PH5, were recently discovered with similar orbits to Cruithne.
Further, and very detailed information on the asteroid Cruithne can be found at http://www.astro.queensu.ca/~wiegert/3753/3753.html